Apparatus for water separation in the vacuum system of a paper machine and method for utilizing the same

ABSTRACT

The invention relates to an apparatus for implementing water separation in the vacuum system of a paper machine. The apparatus is characterized by comprising a guiding baffle structure ( 1 ) connect to an inlet pipe ( 8 ) and a water trap vessel ( 2 ) as well as a droplet separation cell ( 4 ) mounted at the mouth of an outlet pipe ( 9 ).

The invention relates in accordance with the preamble of claim 1 to an apparatus for implementing water separation in the vacuum system of a paper machine. Furthermore, the invention relates to a method in accordance with claim 7.

It is generally known to use vacuum for dewatering a web at the upstream end of a paper/cellulose/cardboard-making machine. The removed water must be separated from the vacuum flow prior to passing the air to a vacuum pump or blower. To this end, a steel tank has conventionally been employed wherein the flow is retarded and water is separated from air utilizing a cyclone concept. For greater air flow volumes concrete tanks have been developed in which separation of water occurs by retarding the flow velocity and then passing the air-water aerosol via droplet separation lamella plates. In the appended drawing (FIG. 1) is shown a typical concrete separation tank embodiment; this kind of construction is used by, e.g., in the structure disclosed in 1985 by the Sulzer Escher Wyss company.

In the state of the art, this construction is employed in conjunction with vacuum systems equipped with turbo blowers. In practice the system is relatively functional, but needs a lot of maintenance by the operator. A particular problem arises from the adherence of pulp to the walls of the tank structure as well as to the droplet separation lamella plates. The separation efficacy is substantially deteriorated when the lamella plates gather a layer of pulp. Resultingly, fiber can pass along with the air flow to the vacuum pump/blower. In turbo blowers the pulp fibers cling to the blade wheel that may thus become unbalanced. Pulp also adheres to the flow passageways of the blower thereby causing loss of vacuum efficacy. Moreover, in certain blower constructions pulp has penetrated into the labyrinth seals between the blade wheels thus causing damage in the blower.

It must further be noted that the prior-art construction has lamella plates located in the center of the separation tank. During system maintenance the operating personnel thereof must have access to the space behind the lamella plates for cleaning the entire tank. The lamella plate compartment must be provided with a door that can be opened during a maintenance shutdown. Cleaning the lamella plates is an extremely lengthy process and, moreover, they are expensive to fabricate.

Another disadvantage is that in practice a long piping must used to connect this kind of concrete separator tank to the blowers. As the vacuum flow takes place at 100% RH and air is cooled in the long piping, condensation occurs. Subsequently, the condensed water causes erosion in the blade wheels of the blower. These problems need be overcome.

Now the present invention offers a solution through a novel kind of apparatus that uses an improved method of water separation in a vacuum system.

The essential features of the invention are an import asset of the apparatus and the method utilizing the same as specified in the claims. More precisely, the invention is characterized by what is disclosed in the appended claims.

The invention is next described in more detail by making reference to the annexed drawings wherein

FIG. 1 shows an embodiment of a prior-art construction;

FIG. 2 shows a preferred embodiment of a construction according to the invention;

FIG. 3 shows a sectional view of a construction according to the invention as seen from above; and

FIG. 4 shows a preferred embodiment of a construction according to the invention.

FIGS. 2 and 3 illustrate an apparatus according to the invention and a method utilizing the same. The invention discloses a novel concept capable of eliminating the disadvantages of the prior art. In FIGS. 2 and 3 the concrete separation tank is shown in both a sectional view and viewed from above along line A-A. The separator tank has a hatched manhole 3 suited for moving the interior structures of the tank therein. The separated water is pumped out by a discharge pump 5.

An essential feature of the invention is that the inlet pipe of the concrete separation tank is provided with a guiding baffle structure 1 that directs water and pulp to the bottom of the separator tank. In this preseparator, the air flow is retarded gradually without invoking a vacuum loss. The guiding baffle structure 1 has a multisectional construction, most advantageously comprising two sections 1A and 1B displaced apart from each other by a gap 10. In gap 10 the flow cross section is twice as large as the flow cross section of inlet pipe 8. In gap 11 the flow cross section is twice as large as the flow cross section of gap 10. The retarding flow directs the water gravitationally down. On the bottom of the preseparator is located a water trap vessel 2 serving to prevent air flow 12 from reaching the tank bottom. In this fashion, air flow 12 is forced to stream along the walls and ceiling of the separator tank, whereby the residual water in the air flow 12 is further separated and thereupon flows down along the tank walls to its bottom.

The tank has no lamella plates at its center, but instead, a droplet separation cell 4 is located at the mouth of the outlet pipe. In droplet separation cells used in the art, air flows in narrow slots thus forcing the droplets to coalesce, whereupon the droplets grown in size fall gravitationally down. The cross-sectional structure of cell 4 can be fabricated using automated manufacturing techniques. According to the invention, the plates of the droplet separation cell are coated with PTFE or some other dirt-repelling material. When required, a small amount of clean water can be sprayed to in front of the cell. In front of the cell and at the outlet pipe end are located plates 6 and 7 serving to prevent direct air flow into the outlet pipe 9.

In FIG. 4 is shown a preferred embodiment of the construction according to the invention wherein four turbo blowers 13 are installed on top of the concrete separation tank. When using lightweight blowers having the blade wheel mounted directly on the drive motor shaft, the installation can be implemented readily on the concrete separation tank described above. This arrangement offers savings in mill footprint and piping costs. Pipe 12 is a short section between the blower and the separation tank, most advantageous only a mere piping bend. When desired, this bend can be insulated thus entirely avoiding condensation therein. FIG. 4 represents a feasible construction showing the blower outlet pipe 9 and the blower inlet pipe 8 connected to the separation tank.

On the basis of the above description, the invention clearly provides significant benefits. Hence, the droplet separation system according to the invention can be manufactured at a lower cost than the prior-art construction illustrated in FIG. 1; moreover, offering an improved separation efficacy and faster maintenance. It is an essential object of the present invention to ease user maintenance tasks and achieve a higher degree of separation. To the end of the invention, correct guidance of air flows in the separation tank, particularly along the walls thereof, is crucially important. As proven by practical test, this feature significantly enhances separation efficacy.

To a person skilled in the art it is obvious that the invention is not limited by the above-described exemplary embodiments, but rather may be varied within the inventive spirit and scope of the appended claims. 

1. An apparatus for implementing water separation in the vacuum system of a paper machine, characterized in that the apparatus comprises a guiding baffle structure connect to an inlet pipe and a water trap vessel as well as a droplet separation cell mounted at the mouth of an outlet pipe.
 2. The apparatus of claim 1, characterized in that the guiding baffle structure is constructed to serve as a preseparator incorporating gaps and of different size for retarding an air flow gradually without causing vacuum loss.
 3. The apparatus of claim 1, characterized in that in gap the flow cross section is twice as large as the flow cross section of inlet pipe and in gap the flow cross section is twice as large as the flow cross section of gap.
 4. The apparatus of claim 1, characterized in that the guiding baffle structure has a multisectional construction, most advantageously comprising two sections and displaced apart from each other by the gap.
 5. The apparatus of claim 1, characterized in that located in front of the droplet separation cell and at the outlet pipe are plates and serving to prevent direct air flow into the outlet pipe.
 6. The apparatus of claim 1, characterized in that the droplet separation cell is fabricated using automated manufacturing techniques and the plates of thereof are coated with PTFE or some other dirt-repelling material.
 7. A method for implementing water separation in the vacuum system of a paper machine, characterized in that in the method a guiding baffle structure adapted to function in conjunction with an inlet pipe separates water and pulp to fall on the bottom of the separator tank, whereby said structure has at its lower end a water trap vessel serving to prevent the air flow from reaching the tank bottom in order to guide the air flow to an outlet pipe via a droplet separation cell located at the mouth thereof.
 8. The method of claim 7, characterized in that said guiding baffle structure functions as a preseparator in such a manner that gaps and formed into the structure retard the air flow gradually without vacuum loss and direct the water gravitationally downwardly to the tank bottom, wherefrom the separated water is pumped out by a discharge pump.
 9. The method of claim 7, characterized in that in the method the air flow is forced to stream along the walls and ceiling of the separator tank, whereby the residual water in the air flow is further separated and thereupon flows down along the tank walls to its bottom.
 10. The method of claim 7, characterized in that in the method the air flow is retarded by way of providing the guiding baffle structure with a multisectional construction, most advantageously comprising two sections and displaced apart from each other by the gap such that gap has a flow cross section twice as large as the flow cross section of inlet pipe and gap has a flow cross section twice as large as the flow cross section of gap.
 11. The apparatus of claim 2, characterized in that in gap the flow cross section is twice as large as the flow cross section of inlet pipe and in gap the flow cross section is twice as large as the flow cross section of gap.
 12. The apparatus of claim 2, characterized in that the guiding baffle structure has a multisectional construction, most advantageously comprising two sections and displaced apart from each other by the gap.
 13. The apparatus of claim 3, characterized in that the guiding baffle structure has a multisectional construction, most advantageously comprising two sections and displaced apart from each other by the gap.
 14. The apparatus of claim 2, characterized in that located in front of the droplet separation cell and at the outlet pipe are plates and serving to prevent direct air flow into the outlet pipe.
 15. The apparatus of claim 3, characterized in that located in front of the droplet separation cell and at the outlet pipe are plates and serving to prevent direct air flow into the outlet pipe.
 16. The apparatus of claim 4, characterized in that located in front of the droplet separation cell and at the outlet pipe are plates and serving to prevent direct air flow into the outlet pipe.
 17. The apparatus of claim 2, characterized in that the droplet separation cell is fabricated using automated manufacturing techniques and the plates of thereof are coated with PTFE or some other dirt-repelling material.
 18. The apparatus of claim 3, characterized in that the droplet separation cell is fabricated using automated manufacturing techniques and the plates of thereof are coated with PTFE or some other dirt-repelling material.
 19. The apparatus of claim 4, characterized in that the droplet separation cell is fabricated using automated manufacturing techniques and the plates of thereof are coated with PTFE or some other dirt-repelling material.
 20. The apparatus of claim 5, characterized in that the droplet separation cell is fabricated using automated manufacturing techniques and the plates of thereof are coated with PTFE or some other dirt-repelling material. 